Objective: The aim of the present study was to investigate risk factors for breast cancer in women under 40 years.during recent 10 years(1998-2007)

Materials and Methods: The study was a descriptive case control analysis one in Imam khomeiny hospital.Cases were 312 women under40 years with histologically confirmed, breast cancer, and controls were 312 women with same age Presenting to hospital for non-neoplastic, non-hormone-related diseases.Both groups were age matched. informations were collected using a short structured questionnaire.Data analysis was performed using Chi square- indipendant T Odda ratios (ORs) and logistic regression test analysis.

Results: There was a significant relationship with marital status, family history of breast cancer, age at first birth, and at menarche, parity, duration of breast-feeding and use of O.C.P,but history of breast-feeding and of abortion were not related. The results of Univariate logistic regression analysis were: in women never married (OR=2/42 %95CI=1/51-3/88)(P<0/001). in women with a family history of the breast cancer (OR=7/07 %95 CI=2/95-16/99) (P<0/001). OR=0/1 (%95CI=0/04-0/23) (P<0/001) for women reporting menarch at the age of≥15years compared with <12years.Breast cancer risk was significantly higher in women with parity ≥4 compared with nulliparity (OR=13/3 95% CI=3/89-45/66) (P<0/001) and was directly associated with age at first birth [OR=1/93 (95%CI=1/02-3/67) (P=0/041)] among women aged≥30 years at first birth compared with these aged<30). No association emerged with history of breast-feeding (p=0/985) and history of abortion (p=0/749), but there was a significantly inverse association between duration of lactation and breast cancer risk (p <0/ 001). For women who breastfed for <24 months OR=1/77 (95% CI=1/22-2/58) when compared with those who breastfed for ≥ 24 months. With reference to oral contraceptives use the or was 2/83 (95%CI=1/87-4/24) (P<0/001) for users. In multivariate logistic regression parity, family history of the breast cancer, use of O.C.P, age at first birth respectively were impacted. in under 40 years breast cancer risk.

Conclusion: The risk was significantly higher in women under the age of 40 with parity ≥4 compared with nulliparity and no association emerged with history of breast-feeding. Other risk factors in this study were similar to those described in epidemiology at any age.